- Identify valve types and their flow control characteristics
- Select gasket materials and apply proper bolt tightening patterns
- Calculate sling angles and safe working loads for rigging
- Implement lockout/tagout procedures for energy isolation
Lesson 1
Control Valves, Check Valves & Relief Valves
Valve Types
| Valve | Function | Flow Control |
|---|---|---|
| Gate | On/off isolation | Full open or full closed only |
| Globe | Throttling/regulating | Variable flow control |
| Ball | Quick on/off | Quarter-turn operation |
| Butterfly | Moderate throttling | Quarter-turn, low pressure drop |
| Check | Prevents backflow | Automatic, one-direction only |
| Relief | Overpressure protection | Opens at set pressure |
Gate Valves Are Not for Throttling
Never use a gate valve in a partially open position for flow control. The partially open gate creates turbulence that erodes the seat and disk, causing premature failure. Use a globe or butterfly valve for throttling service.
Key Takeaway
Gate valves are for on/off isolation only. Globe valves are for throttling. Check valves prevent backflow automatically. Relief valves protect against overpressure. Match valve type to the required service.